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5/3 A New Crop of Eaters

this doe’s baby(s) visibly moved as I took the pic

Our ecosystem engineers have been hard at work (eating) as they get ready to come out with this year’s new and improved model. Natural selection will choose the best of these, just to keep up with a changing world. The most useful adaptational tweak for deer in our forest would be the desire to eat invasive plants only – thereby ensuring an endless food supply.

The same doe reaching for a mouthful of hackberry leaves

The birthing will be soon, and many mamas will have twins, the usual number for a mature healthy doe. At this rate of increase, it’s easy to see how White-tail numbers went from an est. 300,000 in the 1930’s to as many as 30 million this decade. It also makes you wonder just how many more deer are added to our small urban forest each season.

This doe gave birth to her fawn just downhill from the nature center last spring

I still remember when my husband and I saw the first deer tracks at Beargrass Creek SNP. It was only eighteen years ago, and how excited we were – big wild things in the city! (this was before coyotes really moved in). It’s hard to say how big our deer herd is now, except that it’s bigger each year. The only time I’ve had a chance to count a bunch of them together is in winter – a few years ago I counted over 20 as they straggled up to the Nature Center in the evening, to browse the plantings.

With this many large herbivores around, you know they have to be eating more than your hostas. And for deer, eating is mostly what they do. In contrast to predators, who catch (if they’re lucky) a high protein, high fat animal meal that satisfies for awhile – deer must continually process large amounts of greenery.

Like other ruminants, White-tails re-chew what they eat as a “cud”, and can digest even cellulose with help of bacterial microbes. To stay well nourished they must seek out a variety of plants; but their unerring ability to find the few “highly preferred” ones amongst all the others is remarkable (and very frustrating to gardeners and tree planters!)

a yearling browsing on Wintercreeper

Which brings us to the nitty-gritty of this post – when deer are above the carrying capacity of their habitat, something has to give. The deer in our forest are not exactly starving, and are still avoiding most low preference foods such as the invasive Bush Honeysuckle and Privet. But sadly, at the top of the “highly preferred” list is the new growth of young trees such as Hickory, Oak, Hackberry, Sugar and Red maple, Tulip tree, Black Cherry, Elm and Ash. That is – all of our future forest trees (with the exception of weedy Box Elder, which is little browsed). My tongue in cheek label “ecosystem engineer” is quite accurate – White-tails are changing the make-up of future forests.

To illustrate this point, here’s a gallery of young trees that have been browsed repeatedly and will likely never get big. The trees in the pics are all under six feet; the magic number a tree’s height must exceed to be home free. The only way these species could mature in our forest under current conditions would be with a protective cage.

Tuliptree

Red Maple

Red Oak

Hackberry

Bitternut Hickory

Greenbriar (Smilax) – not a tree, but definitely a preferred browse

So what will future forests look like if deer continue their numbers trajectory? Barring a population crash due to disease (such as CWD) – we can expect eastern forests of the future to have a very different composition. As old or diseased trees fall, and fewer young ones replace them, a more open, shrubby landscape may prevail. Unfortunately this will also mean an open niche for non-native plants like Bush Honeysuckle, Privet, Buckthorn and others.

beautiful grassy woodland at BCSNP with very few young trees

But I’m a “make lemonade” kind of thinker – even in a deer-engineered forest there are opportunities for native plants that the deer detest. Think Pawpaw and Spicebush; both are increasing quickly at Beargrass Creek. These two mainstays of the eastern forest solved the browsing dilemma ages ago – their unpleasant tasting chemical compounds even transfer protection to the caterpillars of two butterflies that feed on them, the Spicebush Swallowtail (Spicebush) and the Zebra Swallowtail (Pawpaw).

five year old Spicebush produces its first berries

Tastier natives that grow in clumps, such as Elderberry and Smilax, can be protected with mountains of brush thrown around them.

Elderberry patch sheltered from deer for four years

And then there’s deer repellent. This one is my favorite.

If it seems a bit over the top to go around the forest spraying this foul-smelling liquid, then so be it. We all have our foibles – I like to see young trees survive.

Pretty soon the does will be dropping their offspring, and little fawns will leap up when I least expect them (once they get their legs, they don’t lay still when their cover is blown).